The major objective of this contract is the provision of a mechanism for the development of pertinent information on chemicals nominated to the NTP for toxicological testing as well as on chemicals previously tested by the NTP for one or more toxicological endpoints which may be candidates for further testing. The contractor will accomplish this objective by preparing Executive Summaries on chemicals nominated for extensive testing, by performing class studies of chemicals previously tested by the NTP and of their structural analogs to help identify candidates for additional testing and by entering relevant data into the NTP CHEMTRACK computerized data base on production, uses, exposure, and NTP nomination and evaluation history of chemicals nominated or previously selected for NTP testing.